FR2924489A1 - MAGNETOCALORIC GENERATOR - Google Patents

Abstract

The present invention relates to a generator (1) comprising at least one thermal stage (10) provided with active elements (2) based on magnetocaloric material arranged around a central axis (A) and a magnetic arrangement (3) carried by a driving shaft (30) coinciding with the center axis (A) rotated by an actuator to subject the active elements (2) to a field variation. This generator (1) comprises on both sides of the thermal stage (10) a set of pistons (70) associated with a fluid reservoir (74) for pushing the coolant through the active elements (2), these pistons being driven in alternative translation in chambers (73) by at least one cam (71) coupled in rotation with the motor shaft (30). This generator (1) is characterized in that it comprises forced circulation means (8a) provided with small pinions (80) satellites arranged around the central axis (A), carried by the body (72) of the generator ( 1) and meshing an inner ring gear (81) integral with the cam (71), each pinion (80) forming a mini gear pump stirring the heat transfer fluid and forcing it into said tanks (74) and said chambers ( 73).

Description

TECHNICAL FIELD The present invention relates to a magnetocaloric generator comprising at least one thermal stage provided with active elements based on magnetocaloric material arranged around a central axis, a magnetic arrangement carried by a motor shaft driven in rotation around said axis. central by an actuator, and arranged to subject said active elements to a magnetic field variation, at least one heat transfer fluid contained in said generator, this fluid being pushed through said active elements by pushing means, and at least one chamber of so-called cold exchange and a so-called hot exchange chamber intended to be coupled respectively to external circuits of use.

Prior art:

The magnetic cold technology has been known for more than twenty years and we know the benefits it brings in terms of ecology and sustainable development. Its limits are also known as to its useful calorific power and its efficiency. Therefore, research in this area all tend to improve the performance of such a generator, by playing on the various parameters, such as the magnetization power, the performance of the active elements in magnetocaloric material, the exchange surface between the heat transfer fluid and these active elements, the performance of the heat exchangers, etc.

The magnetocaloric generator described in the previous patent application filed under the number FR 07/07612 by the same applicant comprises one or more thermal modules stacked to form one or more thermal stages, each comprising N active elements in adjacent magnetocaloric material, arranged in a circle around a central axis and subjected to a variation of magnetic field to vary their temperature. These active elements are associated with N pistons driven by an alternating translational movement by a control cam in order to push the heat transfer fluid contained in the thermal module simultaneously in two opposite directions, so that a first fraction of heat transfer fluid is pushed through the active elements subjected to a heating cycle towards a so-called hot chamber, and a second fraction of coolant is pushed through the active elements subjected to a cooling cycle towards a so-called cold chamber and vice versa.

Thus, a number N of mini or micro thermal generators operating simultaneously and in parallel is obtained, making it possible to multiply the surface of exchange between the active elements and the coolant by the coefficient N, thus increasing the heating value of such a generator. . In addition, each magnetic cycle is used optimally since the displacement of the heat transfer fluid in both directions of circulation makes it possible simultaneously to collect the calories produced by the active elements subjected to an increase in the magnetic field (heating cycle) and the frigories produced. by the active elements subjected to a decrease of the magnetic field (cooling cycle), without dead time, nor lost cycle.

Furthermore, other magnetocaloric generators are known in which the coolant is forced into circulation by an external double pump or two external pumps, interposed between the generator and the external circuits including heat exchangers. One of the examples is described in the publication WO 2005/0430052 filed by the same applicant. In this type of generator, the pumps are of a type known per se and must be supplied with power to be able to operate, in particular in electric current, which penalizes the overall energy efficiency of the generator.

Presentation of the invention

The present invention aims to improve the efficiency of a magnetocaloric generator in order to increase its heating value and its economic profitability, while retaining its modular aspect which allows it to be easily configurable according to a specification given in the framework of both industrial and domestic applications.

For this purpose, the invention relates to a magnetocaloric generator of the kind indicated in the preamble, characterized in that it comprises means for forced circulation of the coolant, these means being integrated with said generator and coupled to said motor shaft to be driven by the same actuator as that of said magnetic arrangement.

Thanks to this construction, the generator is equipped with forced circulation means ensuring a mixing of the fluid inside the generator which has the effect of systematically renewing the fluid pushed through the active elements. In addition, these forced circulation means are activated by one and the same actuator. This increases the calorific value of the generator without penalizing its energy efficiency.

According to the embodiments, the forced circulation means can be reported on the generator and / or arranged inside the generator.

In one embodiment, the forced circulation means comprise at least one piston pump provided with a pump body attached to the body of the generator, a receiver shaft coupled in rotation with the drive shaft, at least one piston housed in the pump body and reciprocally controlled by the receiving shaft, and fluid passages communicating the internal volume of the pump with the internal volume of the generator. The control means in alternative translation of said piston by said receiver shaft may comprise a cam transmission.

In the case where the thrust means comprise at least one piston arranged to push the coolant through the active elements and driven in alternative translation by at least one cam coupled in rotation with said drive shaft, the forced circulation means may comprise at least one piston pump provided with at least one central piston freely carried by said motor shaft and driven in alternating translation by said cam. In this case, the cam may be provided with an inner ring gear rotatably coupled to the motor shaft by means of a gear train with planet gears.

The forced circulation means may also comprise small satellite wheels arranged around said central axis, carried by the body of the generator and meshing with an inner ring gear integral with the cam, and fluid passages, each small satellite pinion forming a mini-pump. gear. These forced circulation means may further comprise at least one turbine coupled to said motor shaft.

In another variant embodiment, the forced circulation means may comprise at least one planet pinion meshing with a motor pinion integral with said motor shaft and associated with a pump body provided with heat transfer fluid circulation channels, said satellite pinion associated with said body of pump forming a gear pump.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention and its advantages will appear better in the following description of two embodiments given by way of non-limiting example, with reference to the appended drawings, in which: FIG. 1 is a perspective view of a magnetocaloric generator according to the invention with a thermal stage, FIG. 2 is a view in axial section of the generator of FIG. 1, FIG. 3 is a partial perspective view of a first embodiment of the forced circulation means of FIG. heat transfer fluid of the generator of Figure 1, Figure 4 is an enlarged detail view of Figure 3, Figure 5 is a partial perspective view of a second embodiment of the forced circulation means of the heat transfer fluid, the figure 6 is a perspective view of the pump body forming part of the forced circulation means of FIG. 5, FIG. 7 is a partially cutaway perspective view of a FIG. third embodiment of the forced circulation means for the coolant, FIG. 8 is a plan view of FIG. 7, FIG. 9 is an axial section of FIG. 8 along the IX-IX section line, FIG. an axial sectional view of the generator of FIG. 1 associated with a fourth embodiment of the forced circulation means of the coolant, FIG. 11 is a side view of the forced circulation means of FIG. 10, and FIG. a front view of Figure 11.

Illustrations of the invention and various ways of carrying it out: With reference to FIGS. 1 and 2, the magnetocaloric generator 1 according to the invention, hereinafter referred to as generator 1, comprises at least one thermal stage 10 comprising active elements 2 based on of magnetocaloric material, arranged in a ring around a central axis A, and subjected to a variation of the magnetic field to vary their temperature according to the Carnot cycle, and to create alternately in these active elements 2 a heating cycle and a cycle of cooling. The number of thermal stages 10 is determined according to the specifications of the generator 1, and in particular the desired temperature gradient, each thermal stage 10 can constitute a nestable and stackable module. The magnetic field variation is for example generated by means of a magnetic arrangement 3 disposed inside the active elements 2, rotated about the central axis A by an actuator and associated with a field closing device 4 disposed outside the ring of active elements 2. This magnetic arrangement 3 may comprise permanent magnets or the like, carried by a motor shaft 30 (see FIGS 3 and 7 to 9), symbolized in the other figures by FIG. central axis A, and driven by any type of known actuator (not shown), in continuous rotation or not, alternative or not.

The active elements 2 may be in different forms, namely a crown formed of a single piece or an assembly of adjacent pieces, of geometrical sections or not, perforated or micro-perforated solid material, porous material, powder or agglomerated particles, axially or radially superposed lamellae, etc. from the same magnetocaloric material or an assembly of different magnetocaloric materials, associated or not with other thermally conductive materials.

This generator 1 contains at least one heat transfer fluid arranged to collect the calories and frigories produced by the active elements 2 during successive heating and cooling cycles, and store them respectively in a so-called hot exchange chamber 5 and a chamber so-called cold exchange 6 disposed at the hot and cold ends of said generator closed by lids 50, 60. These exchange chambers 5, 6 are intended to exchange the calories and the frigories collected with external circuits of use via, for example heat exchangers (not shown) connected to tips 51, 61.

More particularly with reference to FIG. 2, this generator 1 comprises, on either side of the thermal stage 10, means 7 for thrusting the heat transfer fluid through the active elements 2, in the form of pistons 70 arranged in view of the active elements 2 and driven in alternative translation by at least one cam 71, integral with the motor shaft, itself driven in rotation about the central axis A by the actuator which controls the rotation of the magnetic arrangement 3. In the case where the generator 1 comprises several thermal stages 10, the thrust means 7 may be common to two consecutive thermal stages 10. These thrusting means 7 are housed in a hollow body 72, which can be arranged to be assembled to the field closing device 4 on the one hand and to the covers 50, 60 on the other hand, in particular by interlocking complementary male shapes. / females, as in the example of Figures 1 to 3. Of course, any other means of assembly can be envisaged, with or without outer casing. In the illustrated example, O-rings or the like (not shown) are interposed between each piece to make this assembly tight, which is held tight by ties 11 or the like, uniformly distributed on the periphery of the generator 1. Still in the example shown in Figure 2, the body 72 is formed in two half-shells assembled radially, defining a chamber 73 for the pistons 70 and a reservoir 74 containing the heat transfer fluid. This body 72 also comprises bearings 75 for guiding the cam 71 in rotation. The cam 71 comprises a cam profile 71a, for example sinusoidal, circulating in a groove 70a formed in each piston 70.

The generator 1 according to the invention differs from the state of the art in that it comprises integrated forced circulation means 8a, 8b, 8c, 8d arranged to create a forced circulation of the coolant at least in the one or more fluid reservoirs 74 and in the chamber or chambers 73 of the pistons 70, depending on whether the generator 1 comprises one or more thermal stages 10, these fluid reservoirs 74 may be communicating or not. These forced circulation means 8a, 8b, 8c, 8d are designed to integrate with said generator 1, either in its internal volume as in the embodiments illustrated in FIGS. 2 to 9, or reported as in the embodiment illustrated in FIGS. Figures 10 to 12. In all cases, they relate to the motor shaft of the magnetic arrangement 3 and are driven by the same actuator, which allows a compact construction and a single power supply.

These forced circulation means 8a, 8b, 8c, 8d make it possible to create a stirring of the coolant in each tank 74, according to a loop cycle or an alternating cycle depending on the type of means used, to mix the fluid before and after its passage. through the active elements 2, namely the fraction of fluid loaded with calories and the fluid fraction charged with frigories, so as to balance the temperature of this fluid in each tank 74, and to constantly renew the fluid in the chambers 73 which is pushed through the active elements 2 by the pistons 70, having the effect of facilitating the creation and maintenance of a temperature gradient between the inlet and the outlet of said active elements 2, and consequently of simultaneously increasing the temperature gradient between two consecutive thermal stages 10, and the overall thermal power of the generator 1.

In the first embodiment illustrated in Figures 2 to 4, the forced circulation means 8a comprise a set of small pinions 80 satellites, arranged in a circle around the central axis A, carried by the body 72 and free to rotate around B axes integral with said body 2. For reasons of clarity, the right part of Figure 2 is refined and does not show the small pinions 80, only a small pinion 80 is shown in Figure 3 and the cam 71 is not shown in the detail of Figure 4. These pinions 80 meshing a ring gear 81 integral with the cam 71 and rotated about the central axis A. The rotation of the cam 71 rotates the ring gear 81 which causes the rotation of the small pinions 80 operating as mini-gear pumps, that is to say, causing by their toothing the heat transfer fluid contained in the tank 74 towards the pistons 70 and the active elements 2, to create a circulat ion of the fluid in loop. For this purpose, the body 72 delimits a pump body 84 for each small pinion 80, and fluid passages 82 (see FIG 4) in the form of channels, grooves, orifices or the like, are formed in the body 72 and in the cam 71 to put into communication, as soon as a passage in one of the chambers 73 opens, the reservoir 74 with the corresponding exchange chamber 5, 6 or a neighboring tank 74 if the generator 1 comprises several thermal stages 10, on the one hand, and with the chamber 73 of the pistons 70 on the other hand. The small pinions 80 are preferably arranged close to the pistons 70. Thus, the fraction of heat transfer fluid pushed through the active elements 2 is renewed continuously. These forced circulation means 8a also comprise a central turbine 83, integral with the cam 71 and rotated about the central axis A to further increase the mixing of the coolant within the tank 74. For this purpose, the cam 71 comprises in the vicinity of the blades of the turbine 83 fluid passages 82 passing through to allow the circulation of the coolant right through the turbine 83 and the cam 71. In this embodiment, the piece constituting the cam 71 combines several functions: the reciprocating translation drive of the pistons 70 to push the coolant through the active elements 2, driving the small pinions 80 to create mini-gear pumps forcing the circulation of the coolant towards the pistons 70 and active elements 2, and the forced mixing of the coolant in the tank 74. Of course and depending on the variants, the cam 71 can t be proposed with or without turbine 83, and with or without the small gables 80.

In the second embodiment illustrated in FIGS. 5 and 6, the forced circulation means 8b comprise at least one satellite pinion 84, and in the example represented three pinions 84 satellites, this number being nonlimiting, arranged in a circle around of the central axis A, at equal distance or not, carried by the body 72 and free in rotation around C integral axes of said body 2. These pinions 84 meshing with a motor pinion 85 (represented by a reference line in the figure 5) integral with the cam 71 and driven in rotation about the central axis A. The rotation of the cam 71 rotates the drive pinion 85 which causes the rotation of the planet gears 84 operating as gear pumps, that is, that is to say causing by their toothing the heat transfer fluid contained in the reservoir 74 in the direction of the pistons 70 and the active elements 2 to create a circulation of the fluid loop. For this purpose, these pinions 84 are associated with a fixed pump body 86 mounted in the body 72, provided with channels 87 for circulating the fluid around each pinion 84 communicating with the fluid passages 82 provided in the cam 71 and the body 72 with reference to the previous example. This pump body 86 also has through-flow fluid passages 88 for allowing the heat transfer fluid to flow through the pump body 86 and the cam 71. In this embodiment, the motor pinion 85 also plays the role of the turbine 83 of the preceding example, that is to say that it increases the mixing of the coolant in the tank 74.

In the third embodiment illustrated in FIGS. 7 to 9, the forced circulation means 8c comprise a central piston 90 animated with an alternative translatory movement to function as a piston pump and to create a circulation of the alternating fluid. This central piston 90 is mounted free in translation and in rotation on the motor shaft 30 of the magnetic arrangement 3. This drive shaft 30 carries a toothed wheel 91 which meshes with one or more pinions 92, arranged in a circle around the axis central A, equidistantly or not, carried by the body 72 and free in rotation about pins D integral with said body 72. These pinions 92 meshing with an inner ring gear 93 rotating a cam 94 about the central axis A The cam 94 has the same function as the cam 71 of the preceding examples and comprises the same type of cam profile 71a circulating in the groove 70a of the pistons 70 to move them in alternative translation and push the coolant into the active elements 2. This cam 94 simultaneously ensures the reciprocating displacement of the central piston 90 by means of a follower pin 95 flowing in a cam path 96 formed at the periphery of the central piston 90, this cam path. 96 having substantially a sinusoidal shape (cf. Fig. 9). The axial stroke of the central piston 90 is limited by the body 72 on one side and the toothed wheel 91 on the other side. As in the previous examples, fluid passages 82 are formed in the body 72 to allow the circulation of the coolant between the reservoir (s) 74 and the chamber 73 of the pistons 70.

In the fourth embodiment illustrated in Figures 10 to 12, the forced circulation means 8d comprise a piston pump 100 attached to one of the covers 50 and provided with a receiving shaft 101 rotatably coupled to the motor shaft (not shown ) around the central axis A, and driven by the actuator of the magnetic arrangement 3. This piston pump 100 comprises a body 102 defining at least one chamber 103 in which at least one piston 104 moves in alternative translation for create a circulation of the alternating fluid. In the example shown, the pistons 104 are four in number, this number not being limiting, each housed in a chamber 103, arranged around the central axis A equidistantly, but not necessarily. For this purpose, the receiving shaft 101 carries a follower pin 105 flowing in a cam path 106 formed in the pistons 104 (see Fig. 12). The axial stroke of the pistons 104 is limited by the walls of the chambers 103. Fluid passages 107 are formed in each chamber 103 of the body 102, in the cover or covers 50 and 60, in the body or bodies 72, to allow the circulation heat transfer fluid between the chambers 103 of the pistons 104 and the inside of the generator 1, namely in the exchange chambers 5 and 6, but also and especially in the tanks 74. The number of pistons 104 is not limiting, it can be provided that each piston 104 is associated with a reservoir 74 in a generator 1 having a plurality of thermal stages 10. According to the alternative embodiments, these forced circulation means 8d can be used alone or in combination with one or the other of forced circulation means 8a, 8b or 8c.

The operation of the generator 1 comprises driving with the same actuator (not shown) the rotation of the magnetic arrangement 3 to create the heating and cooling cycles within the active elements 2, the rotation of the cams 71 to move the pistons 70 in alternative translation so as to push the coolant through said active elements 2, the rotation of the means 8a to 8d to stir the heat transfer fluid in the tanks 74 and put it into forced circulation, to homogenize its temperature between each thermal stage 10. The stacking of several thermal stages 10 thus makes it possible to increase in cascade the temperature gradient between the hot and cold exchange chambers 6 disposed at the ends and designed so that the calories and frigories collected can be conveyed to external circuits of use (heating, air conditioning, tempering, etc.), either by conduction or by heat exchanger (not shown).

The heat transfer fluid used is preferably liquid. We will choose a chemical composition of the heat transfer fluid adapted to the desired temperature range to obtain maximum heat exchange. This fluid can be liquid, gaseous or diphasic. If it is liquid, one will use for example pure water for positive temperatures and water added antifreeze, for example a glycol product or a brine for negative temperatures.

Possibilities of industrial application:

All the parts that make up the generator 1 according to the invention can be produced in series according to reproducible industrial processes. All these parts except active elements 2 and magnetic means 3, 4 can be made of thermally insulating materials molded, injected or the like. The thermal stages 10 may be assembled by any appropriate sealing means and any known suitable fastening means, such as tie rods 11 (see Fig. 1). The construction of the generator 1 by thermal stages 10, compact and stackable, which can be standardized, makes it possible to respond to a wide range of industrial and domestic applications, at competitive costs, in a small footprint, by offering high performance. calorific value not equaled to date with this type of generators.

The present invention is not limited to the embodiments described but extends to any modification and variation obvious to a person skilled in the art while remaining within the scope of protection defined in the appended claims. 13

Claims (10)

claims 1. Magnetocaloric generator (1) comprising at least one thermal stage (10) provided with active elements (2) based on magnetocaloric material arranged around a central axis (A), a magnetic arrangement (3) carried by a shaft motor (30), driven in rotation about said central axis (A) by an actuator, and arranged to subject said active elements (2) to a magnetic field variation, at least one heat transfer fluid contained in said generator (1), this fluid being pushed through said active elements (2) by thrust means (7), and at least one so-called cold exchange chamber (6) and a so-called hot exchange chamber (5) intended to be coupled respectively to external circuits of use, characterized in that it comprises means for forced circulation (8a, 8b, 8c, 8d) of the coolant, these means being integrated with said generator (1) and coupled to said motor shaft (30) for be driven by the same actuator than that of said magnetic arrangement (3). 2. Generator according to claim 1, characterized in that said forced circulation means (8d) are reported on the generator (1). 3. Generator according to claim 1, characterized in that said forced circulation means (8a, 8b, 8c) are arranged inside the generator (1). 4. Generator according to claim 2, characterized in that said forced circulation means (8d) comprise at least one piston pump (100) provided with a pump body (102) attached to the generator (1), a shaft receiver (101) rotatably coupled with said drive shaft (30), at least one piston (104) housed in said pump body (102) and reciprocally driven by said receiver shaft (101), and fluid passages ( 107) communicating the internal volume of the piston pump (100) with the internal volume of the generator (1). 14 5. Generator according to claim 4, characterized in that the reciprocating control means of said piston (104) by said receiver shaft (101) comprise a cam transmission (105, 106). 6. Generator according to claim 3, wherein said thrust means (7) comprise at least one piston (70) arranged to push said heat transfer fluid through said active elements (2) and driven in alternative translation by at least one cam ( 94) coupled in rotation with said drive shaft (30), characterized in that said forced circulation means (8c) comprise at least one piston pump provided with at least one central piston (90) carried freely by said driving shaft ( 30) and driven in alternative translation by said cam (94). 7. Generator according to claim 6, characterized in that said cam (94) comprises an inner ring gear (93) rotatably coupled with said drive shaft (30) by means of a gear train with planet gears (91, 92). 8. Generator according to claim 3, characterized in that said forced circulation means (8b) comprise at least one pinion (84) meshing with a gear motor (85) integral with said drive shaft (30) and associated with a pump body (86) provided with fluid circulation channels (87), said pinion (84) satellite associated with said pump body (86) forming a gear pump. 9. Generator according to claim 3, wherein said thrust means (7) comprise at least one piston (70) arranged to push said heat transfer fluid through said active elements (2) and driven in alternative translation by at least one cam ( 71) coupled in rotation with said drive shaft (30), characterized in that said forced circulation means (8a) comprise small pinions (80) satellites arranged around said central axis (A), carried by the body (72) of the Generator (1) andengrenant inner ring gear (81) integral with said cam (71), and fluid passages (82), each small pinion (80) satellite forming a mini gear pump. 10. Generator according to claim 9, characterized in that said forced circulation means (8a) comprise at least one turbine (83) coupled to said motor shaft (30).